1. Field of the Invention
The present invention relates to a heat exchanger in which two types of heat exchangers are integrated into one body. The present invention is effectively used for a hybrid automobile in which an internal combustion engine and electric motor are combined with each other so as to drive the automobile.
2. Description of the Related Art
In general, it is necessary for a hybrid automobile to have two types of radiators. One is a first radiator to cool an engine coolant circulating in an engine (internal combustion engine), and the other is a second radiator to cool an electric system coolant circulating in an electric motor and a control circuit for the motor.
In this connection, the appropriate coolant temperature and pressure of the engine coolant and those of the electric system coolant are different from each other. Therefore, when both coolants are cooled in the same radiator, the cooling efficiency is deteriorated, that is, cooling both coolants in the same radiator is not advantageous.
In order to solve the above problems, Japanese Unexamined Patent Publication No. 10-111086 discloses the following technique. That is, in a radiator composed of a plurality of tubes, in which coolant is circulating, and header tanks, which are arranged at longitudinal end portions of the tubes and communicating with the tubes, each header tank is separated by a separator (bulkhead) so that a portion in which the engine coolant is circulating and a portion in which the electric system coolant is circulating are separated from each other. In this way, the radiator to cool the engine coolant (which will be referred to as the first radiator hereinafter) and the radiator to cool the electric system coolant (which will be referred to as the second radiator hereinafter) are integrated into one body.
However, in the invention described above, between the first and the second radiator, there is provided a heat insulating region in which no fins are arranged, and there is provided a join plate, the shape and size of which are different from those of the cooling fins, in this heat insulating region.
Therefore, in the invention disclosed in the above patent publication, when the tubes and fins are successively laminated on each other in the case of assembling the radiator, it is necessary to specify a position at which the join plate is arranged. Therefore, the working efficiency is low when the radiator is assembled.
Further, in the invention described in the above patent publication, since the join portion of the separator 10 is located in the header tank 30 communicating with the tubes 20 as shown in FIG. 7, for example, in the process of brazing, even if brazing of the separator 10 to the header tank 30 is defective, it is impossible to repair this defective portion. Accordingly, the yield of the product is lowered.
In the case of brazing, it is preferable that the brazing portion is coated with flux. However, in the invention described in the above patent publication, since the join portion of the separator 10 is located in the header tank 30, the separator 10 must be inserted into the tank 30 from a slit hole formed in the header tank 30 after the separator 10 has been previously coated with flux.
In this case, when the slit hole is excessively larger than the thickness of the separator 10, a large gap is formed between the slit hole and the separator 10, which might cause a defective join. On the contrary, when the slit hole is made relatively small, flux coated on the surface of the separator 10 is removed when inserting the separator 10 into the slit hole. As a result, the separator 10 is defectively brazed to the header tank 30.